IL1R2 and endometriosis: However, the significant decline in serum sIL1RAP levels in endometriosis stages I-II shown in the current study together with the reduced concentration of sIL1R2 shown by our and other previous studies, particularly in stages I-II as well [12,13], clearly point to a significant deficiency in the specific regulatory mechanisms of IL1 at the systemic level in the earliest stages of the disease.